Okay this isn't a topic that you can do a tiny take on. You've had the Tl;Dr already above so before I tell you why Term Limits are a bad idea let me tell you some good ideas. I'll do my best not to write a whole paper though. :)

• The House of Representatives can be enlarged to the point that lobbying loses it effectiveness versus the power of constituents. According to the original ratio of Representatives to people we should have ~10,000 Representatives now. Now I get that some people see that as extreme. That's 1 Representative per 30,000 people. But the current ratios are around 1 Representative per 750,000 people. There's a lot of room for negotiation in there and the number of Representatives is set by law, not the Constitution. Even halving that ratio would make it easier for people to run for office, and easier for people to engage with their Representative. Plus, with modern technology, there's no reason we need to feel beholden to a building. Representatives can spend more time in their district, working in committees and voting remotely.

• Many people are more concerned with senility or operating under outdated knowledge than they are with politics as a career. For this we can institute an Age Cap instead of Term Limits. Like the military we can designate being an elected official as a sensitive job and require retirement after a certain age. (The military requires it at 62) This largely avoids the problems with Term Limits while making sure we aren't choosing a single generation to be the bulk of our Representatives and Senators.

• Lastly, we can take steps to get dark money back out of politics and enforce bribery laws that are already on the books. Sadly though this has turned into an issue for SCOTUS reform and abuse of congressional oversight for the FBI.

So Term Limits. They create three massive problems. The Party becomes the brand instead of the politician. Cycling legislators too often creates an experience issue that can be exploited by lobbyists and party officials. Finally, rich donors and think tanks have more money than the current system has excess legislators. There's more than this but these are the big three poison pills.

When we go to vote we vote based on a politician's brand. It's an American thing among western democracies. Other countries have recognizable party leaders but we're fairly unique in voting by individual name. This makes name recognition the number one hurdle any aspiring politician must get over. And the reason ads use the name they support 10 times in 30 seconds, while almost never mentioning the opponent. And when they do it's in audio/visual scare quotes. It's why incumbents have such an advantage. They've been on your news feed for years building their brand.

Term Limits turns that on its head. As we cycle through politicians there will be very little incumbent advantage. There will be far more people vying for your attention. Which means money. It's very expensive to get your name out there. So whose going to pay that bill? If the candidate isn't wealthy enough then it has to be PACs or the Party. (99% of us are not wealthy enough) Yes candidates can ask for donations, but unless they've got an independent source of name recognition, like being a renowned football coach, people aren't going to be very forthcoming. So we discover the method by which the Party becomes the brand. People need a familiar face to give money to. It's the same reason corporations use well known actors in their ads. Now this means another thing though. If the Party controls the branding, because it's how the money comes in, then the Party controls the money. And this also means they control who the money goes to. They get to pick the party candidate without ever interfering in the vote. This actually already happens to an extent. But Term Limits would pour gas on the fire, making this effect much worse.

So now we have Party chosen legislators we need to move on to the next problem, experience. Career politicians know who to call for technical advice, or at the very least they know when they should seek it. Those connections don't exist with freshmen and junior representatives. They're completely at the mercy of experienced staff, lobbyists, and the party that likely provided their staff. (You want our money, you use our people) For example, with Term Limits, they'd be getting forced out right around the time they figured out which military officer they could rely on for a no bullshit assessment of a weapons program. Then there's experience in crafting legislation.

Just recently SCOTUS had a case about releasing inmates with drug convictions and the eligibility terms. The case hung on the proper English grammar of a list. Only it's SCOTUS so it's actually an exercise in making the grammar twist their way politically. And that's with experienced legislators. We already know how the parties would solve this problem though. Pre-written legislation is a thing in most of our state legislatures. The lobbyists actually write the bill, complete with [insert state name here] type entries. One such example, the HOPE act made it harder for people to get food stamps. The exact same wording, in nine states. This kind of rubber stamp legislature will only get worse with Term Limits. Because politicians need to get re-elected, or at least until they reach their lame duck period. And anyone who doesn't toe the line doesn't get their campaign funded.

Which brings us to point three. Why would a lame duck Representative or Senator keep toeing the line? Because they're human, they probably have a family, and they'd like to get paid to stay in the game doing what they know. It's a lot better then the uncertainty of a career switch, and the Party is always hiring. In fact maxing your term with good behavior could become a pre-requisite for higher party positions. Don't worry there's always an exception for the inordinately wealthy. It's that wealth that's going to pay for the cushy landing of ex legislators in board rooms, think tanks, and party positions across America. The only difference is it might become a time limited deal instead of an actual sinecure like it is now. But it would still be life changing money and networking for most people. The important part here though is you must remain loyal to the party, you must vote the way they tell you to vote, and you must stump for your pre-selected replacement.

The two major parties already have way too much influence in our system. And the natural competitor stops being independent candidates or third parties. It becomes the lobbyists themselves. After all if campaigns become even more aligned with money, then who has more money than private multi national corporations?